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A hinge line is an imaginary longitudinal line along the dorsal edge of the 
A hinge line is an imaginary longitudinal line along the dorsal edge of the shell
Shell may refer to:
Architecture and design
* Shell (structure), a thin structure
** Concrete shell, a thin shell of concrete, usually with no interior columns or exterior buttresses
** Thin-shell structure
Science Biology
* Seashell, a hard o ...
of a bivalve
Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, bival ...
mollusk
Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is e ...
where the two valves
A valve is a device or natural object that regulates, directs or controls the flow of a fluid (gases, liquids, fluidized solids, or slurries) by opening, closing, or partially obstructing various passageways. Valves are technically fittings ...
hinge or articulate. The hinge line can easily be perceived in these images of a mussel shell and an ark shell
Ark clam is the common name for a family of small to large-sized saltwater clams or marine bivalve molluscs in the family Arcidae. Ark clams vary both in shape and size. They number about 200 species worldwide.
The shells of ark clams are of ...
.Invertebrate Paleobiology on-line syllabus on Bivalves, by Dr. Burt Carter, Georgia Southwestern State University, at: http://itc.gsw.edu/faculty/bcarter/paleo/labs/moll/biv2.htm
The hinge teeth
Hinge teeth are part of the anatomical structure of the inner surface of a bivalve shell, i.e. the shell of a bivalve mollusk. Bivalves by definition have two valves, which are joined together by a strong and flexible ligament situated on the hing ...
, structures which control the articulation of the valves, are often but not always situated along the hinge line.
References